title: Secondhand tobacco smoke exposure and heart rate variability and inflammation among non-smoking construction workers: a repeated measures study.
abstract: BACKGROUND
  Although it has been well recognized that exposure to secondhand tobacco smoke (SHS) is associated with cardiovascular mortality, the mechanisms and time course by which SHS exposure may lead to cardiovascular effects are still being explored.
  
  
  METHODS
  Non-smoking workers were recruited from a local union and monitored inside a union hall while exposed to SHS over approximately 6 hours. Participants were fitted with a continuous electrocardiographic monitor upon enrollment which was removed at the end of a 24-hr monitoring period. A repeated measures study design was used where resting ECGs and blood samples were taken from individuals before SHS exposure (baseline), immediately following SHS exposure (post) and the morning following SHS exposure (next-morning).Inflammatory markers, including high sensitivity C-reactive protein (CRP) and white blood cell count (WBC) were analyzed. Heart rate variability (HRV) was analyzed from the ECG recordings in time (SDNN, rMSSD) and frequency (LF, HF) domain parameters over 5-minute periods. SHS exposure was quantified using a personal fine particulate matter (PM2.5) monitor.Linear mixed effects regression models were used to examine within-person changes in inflammatory and HRV parameters across the 3 time periods. Exposure-response relationships with PM2.5 were examined using mixed effects models. All models were adjusted for age, BMI and circadian variation.
  
  
  RESULTS
  A total of 32 male non-smokers were monitored between June 2010 and June 2012. The mean PM2.5 from SHS exposure was 132 μg/m3. Immediately following SHS exposure, a 100 μg/m3 increase in PM2.5 was associated with declines in HRV (7.8% [standard error (SE) =3%] SDNN, 8.0% (SE = 3.9%) rMSSD, 17.2% (SE = 6.3%) LF, 29.0% (SE = 10.1%) HF) and increases in WBC count 0.42 (SE = 0.14) k/μl. Eighteen hours following SHS exposure, a 100 μg/m3 increase in PM2.5 was associated with 24.2% higher CRP levels.
  
  
  CONCLUSIONS
  Our study suggest that short-term SHS exposure is associated with significantly lower HRV and higher levels of inflammatory markers. Exposure-associated declines in HRV were observed immediately following exposure while higher levels of CRP were not observed until 18 hours following exposure. Cardiovascular autonomic and inflammation responses may contribute to the pathophysiologic pathways that link SHS exposure with adverse cardiovascular outcomes.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA. CAVALLARI@uchc.edu.
authors.forename: Jinming
authors.initials: J
authors.lastname: Zhang
authors.forename: Shona C
authors.initials: SC
authors.lastname: Fang
authors.forename: Murray A
authors.initials: MA
authors.lastname: Mittleman
authors.forename: David C
authors.initials: DC
authors.lastname: Christiani
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Cavallari
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000633:toxicity*; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism; D015331:Cohort Studies; D060389:Construction Industry; D004562:Electrocardiography; D006339:Heart Rate / Q000187:drug effects*; D006403:Hematologic Tests; D006801:Humans; D007249:Inflammation / Q000097:blood / Q000139:chemically induced / Q000453:epidemiology*; D008297:Male; D008404:Massachusetts / Q000453:epidemiology; D008875:Middle Aged; D052638:Particulate Matter / Q000633:toxicity*; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D000393:Air Pollutants; D015415:Biomarkers; D052638:Particulate Matter; D014028:Tobacco Smoke Pollution; D002097:C-Reactive Protein